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which is loosely corked, and placed in ice. Whilst triis
solution is cooling to o the diazotoluene chloride is prepared
by adding the powdered sodium nitrite gradually to the j>-
toluidine hydrochloride and stirring. The temperature sliould
not rise above 10. When three-quarters of the nitrite has l>een
added, test occasionally with potassium iodide-starch paper until
a drop gives an immediate deep blue or dark brown colouration.
Add this solution gradually in portions of about 20 c.c. at a. time
to the cold solution of the cuprous chloride, and shake up well
after each addition. A thick crystalline mass of orange coloured
needles, consisting probably of the diazo-copper salt separates,
and, on standing, decomposes slowly, forming a dark-coloured
liquid. After standing a short time, the liquid is distilled in stoa.m.
The distillate is shaken up with a little caustic soda to remove
cresol, and the chlorptoluene, which sinks to the bottom, is
separated. The liquid is further shaken out with a little chloro-
form, which is then added to the chlorotoluene, and the \vliole
dehydrated with calcium chloride. The liquid is decanted, the
chloroform distilled off and the residue collected at 115 - 165.
Yield, about 45 grams.

Properties.  Colourless liquid ; b. p. 162 ; m. p. 7*4
Reactions. Chlorobenzoic Acid.  Boil 10 grams ^-
toluene with 20 grams permanganate dissolved in 500 c.c. of writer
in a brine or calcium chloride bath, with upright condenser, for a
day. The bath should keep the contents of the flask too i ling'
briskly whilst the permanganate is gradually added. Trie oily
drops of chlorotoluene will gradually cease to drip from tlio con-
denser and the permanganate will be nearly decolourised.
The precipitated manganese dioxide is now dissolved a.s sul-
phate by passing in sulphur dioxide gas until the last trace of
brown precipitate has disappeared. The colourless criloro-
benzoic acid comes down in the acid solution on cooling*, and
is filtered, washed with water, and recrystallised from Sjpirit ;
m. p. 236. The yield is theoretical.
CH3.C6H4C1 + 03 = COOH. C6H4C1 + H2O.
See Appendix, p. 284.